This study investigates the short- and long-term consequences of armed conflict and displacement on social cohesion among citizens within attacked nations, using Ukraine and Bosnia and Herzegovina as case studies. Through a pre-registered vignette study in Ukraine (December 2022; N = 1,623), we reveal a significant difference in social cohesion between those who stayed in the country during the war and those who left. This difference intensified when those who left did not want to return. A similar difference persists in Bosnia and Herzegovina 30 years after the Bosnian War (May 2023, N = 338), despite extensive reconciliation efforts. Our findings point towards an understudied consequence of armed conflict and displacement on social cohesion within the attacked nation and shed light on the challenges to post-war reconciliation.